The user interface in form of a window (Window) as a facility to access special program functions in a data program is found in almost every modern interface. The program basing on the use of windows comprises also function keys in e.g. key rows, screen and display delimiters and icons, so-called graphic symbols.
To achieve access to the functions contained in the symbols a cursor is controlled by means of a tracking device (computer mouse, trackball, pointer, etc.) over a display unit showing the symbols, the function of the symbol being produced by e.g. pressing a key with one or several touches.
A problem with the control of the cursor to effect the symbols arises when it is difficult to fix the cursor to the symbol in a distinct way to let the touches have the desired effect.
It is easier to hit e.g. keys situated at the edge of a display than one in its centre. To hit a key at the edge the computer mouse is pulled quickly in the right direction to reach the key. It has no importance if the computer mouse is pulled too far. The cursor will anyhow stop at the edge. To hit a key situated e.g. in the centre of the displays frame more coordination is however required by a user of the computer mouse to hit the target, thus, the user must e.g. slow down the tracking device before the key is reached to let the cursor land on the key. This step takes time and might be difficult and might even give the user stress and irritation.
A further problem, which is related to the use of tracking devices for said object, is that the user requires a simultaneous feature, i.e. to e.g. quickly localize the key for the memorizing function in a program without necessarily having to let the eye scan the display unit.
In the european patent application EP-A1-0,607,580 a computer mouse with a pin is described receiving signals from a host computer unit effecting the pin which generates sensory signals to a users finger top e.g. when the cursor status is altered
The invention according to said EP-application is, however, not without problems in that a finger top must be kept in contact with the pin. Ergonometric studies have shown that the user of a computer mouse when continuously using the computer mouse hardly can keep the finger tops over the same spot over a longer period of time. This is easily understood by ordinary people as some users are easily seized with cramp, writing cramps being a well known complaint. Furthermore, some people suffer from a lighter or heavier trembling. Thus the computer mouse with a pin is restricted in its use for a not negligible part of the users of tracking devices.